The Leiden Convention coronary coding system: translation from the surgical to the universal view

Aims: The Leiden Convention coronary coding system structures the large variety of coronary anatomical patterns; isolated and in congenital heart disease. It is widely used by surgeons but not by cardiologists as the system uses a surgeons' cranial view. Since thoracic surgeons and cardiologists work closely together, a coronary coding system practical for both disciplines is mandatory. To this purpose, the 'surgical' coronary coding system was adapted to an 'imaging' system, extending its applicability to different cardiac imaging techniques.

Methods and results: The physician takes place in the non-facing sinus of the aortic valve, oriented with the back towards the pulmonary valve, looking outward from the sinus. From this position, the right-hand sinus is sinus 1, and the left-hand sinus is sinus 2. Next, a clockwise rotation is adopted starting at sinus 1 and the encountered coronary branches described. Annotation of the normal anatomical pattern is 1R-2LCx, corresponding to the 'surgical' coding system. The 'imaging' coding system was made applicable for Computed Tomography (CT), Magnetic Resonance Imaging (MRI), echocardiography, and coronary angiography, thus facilitating interdisciplinary use. To assess applicability in daily clinical practice, images from different imaging modalities were annotated by cardiologists and cardiology residents and results scored. The average score upon evaluation was 87.5%, with the highest scores for CT and MRI images (average 90%).

Conclusion: The imaging Leiden Convention is a coronary coding system that unifies the annotation of coronary anatomy for thoracic surgeons, cardiologists, and radiologists. Validation of the coding system shows it can be easily and reliably applied in clinical practice.